I wonder if anyone experienced anything like this. I had this car for more than a year.It has 66,500 miles on it. In the last few months I have encountered this problem. While driving at relatively low speed, usually coasting at approximately 20-40 MPH with light pressure on accelerator, the engine sort of shudders and starts to run rough like on 4 or 5 cylinders. It continues to run rough like that indefinitely, I've run 20 or 30 miles like that. When the ignition is shut off and engine is restarted everything returns to normal and the engine runs fine for days or weeks. So far it happened four times. I don't know if the check engine light comes on, who ever owned the car before took the bulb out. I've been to an authorized dealer twice. First time they ran diagnostic check and replaced the front oxygen sensor and a cracked boot on # 2 spark plug. The next day it happened again and I drove it, while it was running rough, to the dealership and showed the condition to the technician. He put the test equipment on and restarted the engine and it was fine. There were no fault codes, nothing in memory, he wanted to do couple more hours for checking and component changing and estimated the bill would run $2500. I decided to hold off on that and consult with somebody.
Does any one know what might be going on. My wife is afraid to drive the car for fear it will die and not restart at all. After four times I'm a little more comfortable but still concerned. I would like to zero in on the problem or I'll have to trade the car.Please help.